Impact of the lateral length scales of dielectric roughness on pentacene organic field-effect transistors

We have shown that the lateral correlation length of dielectric roughness strongly affects the molecular and mesoscale structures and charge transport properties of pentacene. Two series of dielectric surfaces with different lateral characteristics were prepared by a multilayer crosslinking polystyrene (MCPS) method and a plasma etching method. The MCPS surfaces consisted of spike-like structures with dimension of several hundred nanometers, whereas the plasma etched surfaces exhibited bumpy structures with a size about ten times smaller. For both methods, the increase of surface roughness tended to disturb the molecular and mesoscale ordering of pentacene films and reduced their charge carrier mobility. However, the performances of the devices prepared by the plasma etching methods showed a much stronger dependence on the surface roughness than those of the MCPS samples. The average mobilities on the MCPS samples with root mean squar roughness of 3.97 nm were 342 times higher than those on the plasma etching surface with similar roughness values. These results suggested that optimizing the nanostructural surfaces of dielectrics presented an effective approach to improve device performance.